1. Field of the Invention
The present invention relates to a liquid ejection head for ejecting liquid such as ink for recording purposes and a recording apparatus having such a liquid ejection head.
2. Description of the Related Art
Known side shooter type liquid ejection heads have a recording element substrate formed by a substrate and an ejection port plate that are laid one on the other. FIG. 7 illustrates a schematic perspective view of a known liquid ejection head and FIG. 8 illustrates a schematic cross-sectional view of the liquid ejection head taken along cutting line 8-8 in FIG. 7. As seen from FIGS. 7 and 8, a plurality of ejection energy generating elements 102 are arranged on a substrate 101. More specifically, the ejection energy generating elements 102 are arranged in the longitudinal direction of supply port 103 that runs through the substrate 101. On the other hand, a plurality of ejection ports 105 are formed in an ejection port plate 104. The ejection ports 105 are arranged respectively vis-a-vis the ejection energy generating elements 102. A flow path 106 is formed between the ejection energy generating elements 102 and the ejection ports 105. Japanese Patent Application Laid-Open No. H11-138817 discloses a liquid ejection head having such a structure, of which the ejection port plate is made to have a uniform thickness. FIGS. 9A through 9D are schematic cross-sectional views of a liquid ejection head disclosed in Japanese Patent Application Laid-Open No. H11-138817, illustrating steps of manufacturing the liquid ejection head. Referring to FIGS. 9A through 9D, firstly resin layers 203a and 203b that can be dissolved are formed on a substrate 201 that bears ejection energy generating elements 202 formed therein (see FIG. 9A). Then, a resin layer 204 that is to operate as ejection port plate is laid on the substrate 201 and the resin layers 203a and 203b (see FIG. 9B). With this operation, the resin layer 204 can be laid to represent a uniform thickness because the resin layer 203b operates as a base. Thereafter, ejection ports 205 are formed along with a groove 206, or an oblong recess, that is formed in order to remove the resin layers 203a (see FIG. 9C) in a latter step. Finally, the resin layers 203a and 203b are removed and a supply port 207 is produced (FIG. 9D). At this time, a flow path 208 is produced as the resin layer 203b is removed by way of the ejection ports 205.
In the liquid ejection head illustrated in FIGS. 9A through 9D, the linear expansion coefficient of the substrate 201 differs from the linear expansion coefficient of the ejection port plate 204. Therefore, due to environment changes such as heat generation or conservation condition, thermal stress occurs along the interface of the substrate 201 and the resin layer (ejection port plate) 204. Then, as a result, the resin layer 204 can come off from the substrate 201. Japanese Patent Application Laid-Open No. 2003-80717 proposes a liquid ejection head that solves such a problem. FIG. 10 is a schematic perspective view of a liquid ejection head described in Japanese Patent Application Laid-Open No. 2003-80717. As illustrated in FIG. 10, the ejection port plate 302 that is laid on a substrate 301 has a groove 304, or an oblong recess, like the liquid ejection head illustrated in FIG. 9D. In the instance of the liquid ejection head illustrated in FIG. 10, the thermal stress that the ejection port plate 302 undergoes is alleviated by making the groove 304 have oppositely disposed and corrugated side wall surfaces having saw edged ridges and furrows (aperture side walls of the groove 304).
Meanwhile, foreign objects such as dust can adhere to the surface (nozzle surface) of the ejection port plate of a liquid ejection head of the type under consideration as the recording apparatus including the liquid ejection head is operated. When a recording operation is conducted in a condition where foreign objects are adhering to the ejection port plate, some properties of the surface of the ejection port plate such as wettability can be altered by the adhering foreign objects. Then, the ejection ports can be clogged by foreign objects to by turn give rise to faulty ejections. To avoid such a problem, some recording apparatus of the type under consideration are provided with a wiping member for wiping off the foreign objects adhering to the surface of the ejection port plate.
In a liquid ejection head disclosed in Japanese Patent Application Laid-Open No. 2003-80717, the side wall surfaces of groove 304 are corrugated so as to produce saw-edged ridges and furrows as illustrated in FIG. 10. Therefore, as foreign objects are caught between the oppositely disposed side wall surfaces of the groove 304, the caught foreign objects can neither be released nor removed with ease. Thus, if a wiping member is provided, the caught foreign objects may neither be released nor removed. FIG. 11A schematically illustrates a foreign object that is caught by the groove arranged in a liquid ejection head described in Japanese Patent Application Laid-Open No. 2003-80717. The ink ejected from ejection ports 303 can adhere to the foreign object 400 caught in the groove 304. If the foreign object 400 is left there for a long period of time, ink will adhere to the foreign object 400 each time the liquid ejection head is driven to eject ink. Then, the foreign object 400 eventually grows into an ink ball 401 as shown in FIG. 11B. The ink ball 401 that is produced as the foreign object 400 grows can get into one of the ejection ports 303 to give rise to faulty ejections (see FIG. 11C).